1. Field of the Invention
This invention relates to an electrical control circuit and more particularly to a laser diode power supply current control circuit.
2. Description of the Prior Art
Many different types of current control circuits have been developed for use with electronic equipment. However, the unique problems associated with certain laser diode technology has not been solved with prior circuitry. One of these problems has been that the power output of a laser diode decreases as it ages and it is desirable to maintain a constant power level over its entire life cycle. It is also important that the control circuit have the ability to inhibit laser output by an external control level and be free of transient voltages which might damage the laser diode during turn on and off. The present invention overcomes these difficulties by employing a proportional controller which drives a series pass transistor to regulate laser diode current and thus the intensity of the laser diode output. A silicon detector located near the laser provides a current output proportional to laser power for feedback purposes.